The present invention relates to a method and apparatus for an electrohydraulically controlled automatically shifting transmission and, more particularly, to a method and apparatus for a motor vehicle automatic shift transmission in which upshifting during a driving operation is delayed by a first time period if a speed of change of the throttle valve signal falls below a first limit value.
Conventional automatic transmission control systems of motor vehicles driven by internal-combustion engines initiate an upshift, as a rule, when the accelerator pedal is taken back. However, this is not always desirable during cornering or braking since load changes of this type, under certain circumstances, may result in unsafe driving conditions or, when the motor vehicle is accelerated again, one or several backshifts must be forced by giving more gas.
In this context, it is known from DE-PS 33 41 652 to avoid these upshifts at road bends by sensing the lateral acceleration of the motor vehicle. However, this only makes it possible to avoid a shifting at road bends.
It is, therefore, an object of the present invention to provide a method and apparatus for controlling an automatically shifting transmission which is capable of carrying out shifts (gear step changes) which are appropriate for respective situations.
This object has been achieved by utilizing a method and apparatus which delays upshifting during the drive operation by a first time period if a speed of change of the throttle valve signal falls below a first limit value.
Principal advantages of the present invention are that a method and apparatus for the control of an automatically shifting transmission are provided which, particularly in road bends, in front of road bends and during braking, carries out shifts which are appropriate for the respective situation.
The object and advantages are achieved by an expenditure, which is only slightly higher, of operating or driving parameters to be detected by sensors so that an already existing transmission control device for an electrohydraulic transmission, such as model 4HP22 of ZF Co., can be adapted to the present invention without any major expenditures. In addition to only one additional sensor, only a change of the control method is required.